It is known that, in order to meet the demand for higher bit rates offered by wireless communication networks, the wireless communication industry is developing an enhanced version of the Long Term Evolution (LTE) standard known as LTE-Advanced. LTE-Advanced is a preliminary mobile (cellular) communication standard, which was submitted as a candidate Fourth Generation (4G) system to the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) in late 2009, and which is expected to be finalized in 2011. As is also known, the ITU-T manages standards for the ITU. Also, LTE-Advanced is standardized by the 3rd Generation Partnership Project (3GPP) as an enhancement of the 3GPP LTE standard.
It is known that different coordinated multipoint (CoMP) transmission techniques are being considered for LTE-Advanced networks. CoMP techniques provide significant improvements in average and/or edge-user throughput. In a downlink aspect of CoMP (i.e., base station to user mobile terminal link), it is required that multiple mutually remote base stations jointly transmit data to one or more user mobile terminals. CoMP transmission techniques are generally described, for example, in D. Samardzija et al., “An Experimental Downlink Multiuser MIMO System with Distributed and Coherently-Coordinated Transmit Antennas,” IEEE ICC, Glasgow, Scotland 2007; and M. K. Karakayali et al., “Network Coordination for Spectrally Efficient Communications in Cellular Systems,” IEEE Wireless Communications, vol. 13, no. 4, pp. 56-61, August 2006, the disclosures of which are incorporated by reference herein.
In order to perform the downlink CoMP transmission, the network must have knowledge of all the channel states between base station and mobile terminal antennas, for all the mobile terminals that are the subject of the CoMP transmission, i.e., recipients of the CoMP transmission. Each mobile terminal performs downlink channel state estimation, e.g., pilot-assisted estimation using pilots broadcasted by the base stations. Channel state estimation is generally described, for example, in D. Samardzija et al., “Pilot Assisted Estimation of MIMO Fading Channel Response and Achievable Data Rates,” IEEE Transactions on Signal Processing, Special Issue on MIMO, vol. 51, pp. 2882-2890, November 2003; and Feedback Overhead for DL CoMP, 3GPP TSG RAN WG1 #59bis Meeting, Alcatel-Lucent, Alcatel-Lucent Shanghai Bell, January 2010, the disclosures of which are incorporated by reference herein. The channel state estimates, also referred to as channel state information (CSI), are then fed back to the base station over the uplink (i.e., user mobile terminal to base station link). However, the uplink CSI feedback traffic is an overhead which lowers the throughput of the user data traffic.